Light emitting device and manufacturing method thereof

ABSTRACT

Provided are a light emitting device and a manufacturing method thereof. The light emitting device comprises a first conductive semiconductor layer with a lower surface being uneven in height, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser. No. 12/123,910 filed on May 20, 2008, which claims priority under 35 U.S.C. 119(a) to Korean Patent Application No. 10-2007-0049026 (filed on May 21, 2007), each of which is hereby incorporated by reference in its entirety.

BACKGROUND

The present embodiments relate to light emitting devices and manufacturing methods thereof.

Light emitting diodes (LED) using nitride material semiconductors are being widely used as light emitting devices, but require much research and development to improve light emitting efficiency.

SUMMARY

Embodiments provide light emitting devices with improved light emitting efficiency, and manufacturing methods thereof.

Embodiments also provide light emitting devices with minimal internal light loss.

In an embodiment, a light emitting device comprises: a first conductive semiconductor layer with a lower surface being uneven in height, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer.

In an embodiment, a light emitting device comprises: a substrate, a first buffer layer on portions of the substrate, a first undoped GaN layer on the first buffer layer, a first conductive semiconductor layer over the substrate, an active layer over the first conductive semiconductor layer, and a second conductive semiconductor layer over the active layer.

In an embodiment, a method for manufacturing a light emitting device, the method comprising: forming a first buffer layer and a first un-doped GaN layer on a substrate, exposing a portion of the substrate through etching the substrate with the first buffer layer and the first un-doped GaN layer formed thereon, and forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer over the substrate.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 8 are views for describing light emitting devices and manufacturing methods thereof according to present embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, it will be understood that when a layer (or film) is referred to as being ‘on’ another layer or substrate, it can be directly on the other layer or substrate, or indirectly on the other layer, with intervening layers present. Further, it will be understood that when a layer is referred to as being ‘under’ another layer, it can be directly under the other layer, or indirectly under the other layer, with one or more intervening layers present.

In the drawings, the respective layers may be exaggerated in terms of thickness and size, omitted, or schematically shown, for the sake of explanatory convenience and concision. Also, the respective elements are not depicted to scale, overall.

Reference will now be made in detail to light emitting devices and manufacturing methods thereof according to present embodiments, examples of which are illustrated in the accompanying drawings.

FIGS. 1 to 8 are views for describing light emitting devices and manufacturing methods thereof according to present embodiments.

Referring to FIG. 1, a substrate 10 is prepared, and a first buffer layer 20 is formed on the substrate 10.

The substrate 10 may be formed of one of sapphire (Al₂O₃), silicon carbide (SiC), silicon (Si), gallium arsenic (GaAs), zinc oxide (ZnO), and magnesium oxide (MgO), and the first buffer layer 20 may be formed of one of an AlInN structure, an AlInN/GaN stacked structure, an In_(x)Ga_(1-x)N/GaN stacked structure, and an Al_(x)In_(y)Ga_(1-(x+y))N/In_(x)Ga_(1-x)N/GaN stacked structure.

Referring to FIG. 2, a first un-doped GaN layer 30 is formed on the first buffer layer 20.

The first un-doped GaN layer 30 is formed by supplying 40˜50 sccm of trimethylgallium (TMGa) and 30,000 sccm of NH₃ at a growing temperature of 1040˜1050° C. Here, a purge gas and carrier gas of N₂ and H₂ may be used.

While NH₃ and trimethylgallium (TMGa) are generally supplied at a ratio of 1:0.005 to grow an un-doped GaN layer, in the present embodiment, NH₃ and trimethylgallium (TMGa) are supplied at a ratio of between 1:0.0013 and 1:0.0016 to grow the first un-doped GaN layer 30.

The first un-doped GaN layer 30 is unevenly formed on the first buffer layer 20, to resemble an uneven arrangement of hexagonal rods. The first un-doped GaN layer 30 may be formed at a thickness of approximately 1 μm.

Referring to FIG. 3, substrate 10 with the first un-doped GaN layer 30 and the first buffer layer 20 formed thereon is cooled at a temperature of 15˜25° C., after which a dry etch is performed without the use of a mask. Accordingly, the substrate 10, the first buffer layer 20, and the first un-doped GaN layer 30 are unevenly etched.

The dry etch may be performed in an inductively coupled plasma (ICP) etching apparatus.

The etch conditions may be, for example, 1 mTorr of pressure, 25 sccm of BCl₃ gas, 700 W of ICP power, 230 W of chuck power, and 3 minutes of etching time.

As shown in FIG. 3, in portions where the first un-doped GaN layer 30 is formed thin, recesses are formed in the substrate 10 where portions of first buffer layer 20 and the substrate 10 are removed.

Also, in portions where the first un-doped GaN layer 30 is formed thick, only the first buffer layer 20 is present on the substrate 10, or the first buffer layer 20 and the first un-doped GaN layer 30 are present.

Referring to FIG. 4, after the dry etch is performed, a second buffer layer 40 and a second un-doped GaN layer 50 are formed.

The second buffer layer 40 may be formed of one of an AlInN structure, an AlInN/GaN stacked structure, an In_(x)Ga_(1-x)N/GaN stacked structure, an Al_(x)In_(y)Ga_(1-(x+y))N/In_(x)Ga_(1-x)N/GaN stacked structure, an InGaN/GaN superlattice structure, and an AlGaN/GaN superlattice structure.

The second un-doped GaN layer 50 may be formed by supplying 40˜50 sccm of trimethylgallium TMGa and 30,000 sccm of NH₃ at a growing temperature of 1040˜1050° C.

In another method, the second un-doped GaN layer 50 may be formed by supplying 145 sccm of trimethylgallium TMGa and 30,000 sccm of NH₃ at a growing temperature of 1070° C.

As shown in FIGS. 7-8, either an In-doped GaN layer (51) that is doped with indium (In) may be formed on the second un-doped GaN layer 50, or an In-doped GaN layer (52) doped with In may be formed without forming the second un-doped GaN layer 50.

Thus, portions of the substrate 10 may have the substrate 10, second buffer layer 40, and second un-doped GaN layer 50 formed thereon in a vertical direction.

Also, portions of the substrate 10 may have the substrate 10, second buffer layer 40, and In-doped GaN layer formed thereon in a vertical direction.

Further, portions of the substrate 10 may have the substrate 10, second buffer layer 40, second un-doped GaN layer 50, and In-doped GaN layer formed thereon in a vertical direction.

Still further, portions of the substrate 10 may have the substrate 10, first buffer layer 20, first un-doped GaN layer 30, second buffer layer 40, and second un-doped GaN layer 50 formed thereon in a vertical direction.

Yet further, portions of the substrate 10 may have the substrate 10, first buffer layer 20, first un-doped GaN layer 30, second buffer layer 40, second un-doped GaN layer 50, and In-doped GaN layer formed thereon in a vertical direction.

Even further, portions of the substrate 10 may have the substrate 10, first buffer layer 20, first un-doped GaN layer 30, second buffer layer 40, and In-doped GaN layer formed thereon in a vertical direction.

Yet still further, portions of the substrate 10 may have the substrate 10, first buffer layer 20, second buffer layer 40, and second un-doped GaN layer 50 formed thereon in a vertical direction.

Yet even further, portions of the substrate 10 may have the substrate 10, first buffer layer 20, second buffer layer 40, second un-doped GaN layer 50, and In-doped GaN layer formed thereon in a vertical direction.

Additionally, portions of the substrate 10 may have the substrate 10, first buffer layer 20, second buffer layer 40, and In-doped GaN layer formed thereon in a vertical direction.

Referring to FIG. 5, a first conductive semiconductor layer 60, an active layer 70, and a second conductive semiconductor layer 80 are sequentially formed.

The first conductive semiconductor layer 60 may be formed as a silicon (Si)-doped GaN layer or an Si—In-co-doped GaN layer. Also, a low-mole In_(x)Ga_(1-x)N layer may be formed on the SiIn co-doped GaN layer.

By, forming the low-mole In_(x)Ga_(1-x)N layer before the active layer 70 is grown, strain on the active layer 70 can be controlled, and quantum efficiency can be increased.

The active layer 70 may be an InGaN layer formed by supplying NH₃, trimethylgallium TMGa, and trimethylindium TMIn. For example, the active layer 70 may be formed as an InGaN well layer/InGaN barrier structure with a mole ratio difference in each element of InGaN.

The second conductive semiconductor layer 80 is formed on the active layer 70.

The second conductive semiconductor layer 80 may be formed of a magnesium (Mg) doped GaN layer.

Referring to FIG. 6, the second conductive semiconductor layer 80, the active layer, and the first conductive semiconductor layer 60 are selectively etched.

Then, a first electrode layer 90 is formed on the first conductive semiconductor layer 60, and a second electrode layer 100 is formed on the second conductive semiconductor layer 80.

Accordingly, as shown in FIG. 6, a light emitting device 200 is formed.

The light emitting device 200 emits light generated from the active layer 70 when power is supplied to the first electrode layer 90 and the second electrode layer 100.

In the light emitting device 200 according to present embodiments, because the bottom of the first conductive semiconductor layer 60 is unevenly formed, light emitted downward from light generated from the active layer 70 is not lost within the light emitting device 200, and is scattered in the directions indicated by the arrows and emitted outward.

Accordingly, loss of light within the light emitting device 200 can be minimized, thus increasing light emitting efficiency.

The light emitting device 200 according to present embodiments has a substrate 10 formed with recesses of uneven depths and positions, to induce scattering of light generated by the active region 70 and increase light emitting efficiency.

The light emitting device 200 according to present embodiments includes all or a portion of a first buffer layer 20, a first un-doped GaN layer 30, a second buffer layer 40, a second un-doped GaN layer 50, and an In-doped Gan layer between a substrate 10 and a first conductive semiconductor layer 60, in order to induce scattering of light generated by the active layer 70.

Any reference in this specification to “one embodiment,” “an embodiment,” “exemplary embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with others of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

What is claimed is:
 1. A light emitting device, comprising: a substrate having a first surface and a second surface, wherein the first surface is flat surfaces and the second surface is uneven surfaces; a first conductive semiconductor layer on the substrate and having an irregularly uneven lower surface facing the surfaces of the substrate; a buffer layer and a semiconductor layer alternately interposed between the substrate and the first conductive semiconductor layer; an active layer on the first conductive semiconductor layer; and a second conductive semiconductor layer on the active layer, wherein the buffer layer includes a first buffer layer and a second buffer layer, and wherein the first buffer layer is only disposed on the flat surfaces of the first surface of the substrate.
 2. The light emitting device according to claim 1, wherein the semiconductor layer includes a first un-doped GaN (gallium-nitride) layer and a second un-doped GaN (gallium-nitride) layer.
 3. The light emitting device according to claim 2, wherein the first and the second buffer layers, the first and the second un-doped GaN (gallium-nitride) layers are alternately stacked on the substrate.
 4. The light emitting device according to claim 3, wherein the first un-doped GaN (gallium-nitride) layer is only formed on the first buffer layer.
 5. The light emitting device according to claim 1, wherein the first and the second buffer layers includes In (indium).
 6. The light emitting device according to claim 1, wherein the uneven surfaces of the second surface are formed between the flat surfaces of the first surface.
 7. The light emitting device according to claim 1, wherein the first surface of the substrate is higher than the second surface of the substrate.
 8. The light emitting device according to claim 1, wherein the semiconductor layer is a single layer and the single layer is an un-doped GaN layer.
 9. The light emitting device according to claim 8, wherein the first buffer layer, the second buffer layer and the un-doped GaN layer are alternately stacked on the substrate.
 10. The light emitting device according to claim 1, wherein the semiconductor layer includes an un-doped GaN (gallium-nitride) layer and an In-doped GaN (gallium-nitride) layer.
 11. The light emitting device according to claim 10, wherein the first and the second buffer layers, the un-doped GaN (gallium-nitride) layer and the In-doped GaN (gallium-nitride) layer are alternately stacked on the substrate.
 12. A light emitting device, comprising: a substrate having a first surface and a second surface, wherein the first surface is flat surfaces and the second surface is uneven surfaces; a first conductive semiconductor layer on the substrate and having an irregularly uneven lower surface facing the upper surface of the substrate; a buffer layer and a semiconductor layer alternately interposed between the substrate and the first conductive semiconductor layer; an In—GaN semiconductor layer on the first conductive semiconductor layer; an active layer on the In—GaN semiconductor layer; and a second conductive semiconductor layer on the active layer, wherein the buffer layer includes a first buffer layer and a second buffer layer, and wherein the first buffer layer is only disposed on the flat surfaces of the first surface of the substrate.
 13. The light emitting device according to claim 12, wherein the semiconductor layer includes a first un-doped GaN (gallium-nitride) layer and a second un-doped GaN (gallium-nitride) layer.
 14. The light emitting device according to claim 13, wherein the first and the second buffer layers, the first and the second un-doped GaN (gallium-nitride) layers are alternately stacked on the substrate.
 15. The light emitting device according to claim 13, wherein the first un-doped GaN (gallium-nitride) layer is only formed on the first buffer layer.
 16. The light emitting device according to claim 12, wherein the uneven surfaces of the second surface are formed between the flat surfaces of the first surface.
 17. The light emitting device according to claim 12, wherein the first surface of the substrate is higher than the second surface of the substrate.
 18. The light emitting device according to claim 12, wherein the semiconductor layer is a single layer and the single layer is an un-doped GaN layer.
 19. The light emitting device according to claim 18, wherein the first buffer layer, the second buffer layer and the un-doped GaN layer are alternately stacked on the substrate.
 20. The light emitting device according to claim 12, wherein the semiconductor layer includes an un-doped GaN (gallium-nitride) layer and an In-doped GaN (gallium-nitride) layer. 